Injection of anhydrous ammonia into the soil is a commonly used method of supplying nitrogen fertilizer to grain and other crops using an applicator-vehicle pulled by a tractor. An ammonia storage tank is pulled behind the applicator. A hose connects the storage tank to the distribution system on the applicator. The distribution system splits the ammonia into separate lines which feed several knives. These knives are lowered into the soil several inches and ammonia is injected into the ground at the bottom of the knives as the knives are pulled through the soil.
It is normally desired that ammonia be applied uniformly over a field. One of the main problems is achieving this uniformity is difficulty in controlling a stream of mixed liquid and gaseous ammonia. Gaseous ammonia causes many flow sensors to supply incorrect data and causes many pump designs to become vapor locked. Refrigeration of the ammonia and pressurizing with a pump are methods of keeping liquid anhydrous ammonia below its saturation temperature.
A typical use of refrigeration is described in U.S. Pat. No. 4,458,609 to Tofte. A part of the liquid ammonia is used as a refrigerant to cool the inlet liquid stream. This is accomplished in a heat exchanger which mechanically separates the stream of inlet liquid ammonia from a stream of coolant ammonia. Typically, the coolant stream taken from the main stream passes through a restriction, losing pressure. The lower pressure, lower temperature stream provides the cooling for the inlet liquid ammonia.
Another method of cooling the liquid ammonia stream is the use of an externally powered refrigeration system, described in U.S. Pat. No. 6,269,757 to Kiest.
Pressurization of liquid ammonia for agricultural application is typically described in U.S. Pat. No. 5,845,592 to Ridgley and U.S. Pat. No. 6,283,079 to Swanson.
This invention relies on separation of gaseous ammonia from the liquid ammonia flow stream. Prior patents cover the separation of the gaseous phase for agricultural use. However, their methods and purposes are quite different from this invention. A typical example is U.S. Pat. No. 4,069,029 to Hudson which discusses the adiabatic expansion of anhydrous ammonia in an expansion chamber. This expansion creates a significant amount of gaseous ammonia. The gas and liquid are separated and utilized at relatively low pressures, generally close to ambient. The resulting liquid remains in a saturated state so that subsequent pressure drops create more gaseous ammonia. This approach is not useful as a method of feeding pumps or other flow control systems. Other similar patents are U.S. Pat. No. 3,978,681 to Kjelgaard et al, U.S. Pat. No. 4,175,394 to Wiesboeck, U.S. Pat. No. 4,169,677 to Luria, U.S. Pat. No. 4,202,283 to Wiesboeck, U.S. Pat. No. 4,310,344 to Kjelgaard et al, U.S. Pat. No. 4,310,555 to Kjelgaard et al, U.S. Pat. No. 4,341,168 to Siebert, U.S. Pat. No. 4,385,500 to Kjelgaard et al, U.S. Pat. No. 4,657,568 to Jones and U.S. Pat. No. 4,900,339 to Ward et al.
U.S. Pat. No. 6,117,217 to Jones removes gaseous ammonia from a pumped liquid stream. However, it separates out the gas phase after the pump inlet rather than before the inlet. This method requires a particular pump design. Many pump designs would become vapor locked with a mixed phase feed of gas and liquid as described in the patent.